Sea Castle in Sidon (Saida), Lebanon

Built by the Crusaders in 1228, the Sea Castle, connected to the mainland by a fortified Arab stone causeway, sits around 80m offshore on a small island that was formerly the site of a temple to Melkart, the Phoenician version of Hercules. One of many coastal castles built by the Crusaders, it was largely destroyed by the Mamluks to prevent the Crusaders from returning to the region, but its renovation was ordered by Fakhreddine in the 17th century. The building consists of two towers joined together by a wall. The rectangular west tower, to the left of the entrance, is the best preserved, measuring 21m by 17m, and has a large vaulted room scattered with old carved capitals and rusting cannonballs. A winding staircase leads up to the roof, where there is a small, domed Ottoman-era mosque. From the roof there is a great view across the old city and fishing harbour. The east tower isn't as well preserved and was built in two phases; the lower part dates to the Crusader period, while the upper level was built by the Mamluks. On summer days when the shallow water surrounding the castle is calm, you can see many broken columns of rose granite lying on the sea floor; archaeologists believe there's much more to be discovered further off Sidon's coast.